A while ago, I opened a bug report regarding this issue, and it was closed with the note that a fix would be included in 1.9.7 release.
I tested the public release 1.9.10 and noticed the following:
- Previewing an RTL Heading 1 works correctly — it and the following subheadings are right-aligned.
- However, previewing RTL subheadings individually still results in them being left-aligned.
Steps to reproduce

Did you follow the troubleshooting guide? [Y/N]
Yes.
Expected result
RTL Headings to be right-aligned.
Actual result
RTL subheadings are left-aligned in Outline Preview sidebar.
Environment
SYSTEM INFO:
Obsidian version: v1.9.10
Installer version: v1.9.10
Operating system: Windows 11 Pro 10.0.26100
Login status: not logged in
Language: en
Insider build toggle: off
Live preview: on
Base theme: adapt to system
Community theme: none
Snippets enabled: 0
Restricted mode: on
RECOMMENDATIONS:
none